1. Field of the Invention
The present invention is directed to a screen assembly for vibrating screen machinery. In particular, the present invention is directed to a vibrating screen assembly for vibrating machinery having a tubular frame, a self alignment mechanism to align a perforated plate and accompanying screens on a frame, and a seal to prevent leakage of fluid between adjoining screen assemblies.
2. Prior Art
Vibrating shakers utilize a screen assembly or a plurality of screen assemblies to separate solid material from liquids and fine solid particles. The screen assembly is typically secured in and to the vibrating machinery through use of a frame. In some cases, a single screen assembly will be utilized while in other cases, a plurality of screen assemblies will be aligned adjacent to each other end-to-end. The screen assembly is removably attached to the vibrating shaker. A mixture of materials is delivered or fed to the top of the screen assembly. The screen assembly is vibrated by a motor at a high frequency.
The force of gravity plus the vibration of the screen assembly separates the liquid from particles larger than the pore size made up by the combination of layers. This pore size is called the xe2x80x9ccut point.xe2x80x9d The screen assembly may be inclined when secured in the vibrating shaker so that the solids larger than the cut point will move across the screen where they are gathered and disposed of. In other arrangements, one screen assembly is oriented in the shaker in angular relation to the other screen assembly. In each case, the liquid and particles smaller than the cut point pass through the screen assembly and are also collected.
Vibrating shaker machines are often used at remote locations, such as oil and gas well drilling sites. Thus, the replacement screen assemblies must be transported great distances to these remote locations. A relatively lightweight screen assembly is therefore desirable.
Since the screen assembly must be transported and then installed in the field, any sharp edges on the screen assembly should be minimized.
There are various types of screen assemblies having various frames. In one configuration, a plurality of screen cloth layers are attached to a perforated plate which is, in turn, connected to the frame. The perforated plate has a large number of small openings to minimize the unsupported spans of screen cloth. It is important to achieve good adhesion between the perforated plate and the frame. Thus, the frame must have an adequate planar surface to attach securely to the perforated plate.
The screen assembly is subject to tremendous stresses caused by the machinery vibrating it. Additionally, the screen assembly is subject to stresses from the weight of the material to be separated on the top layer of the screen. It is known that the screen assemblies will wear from usage and have a certain useful life, often in hours.
In order to balance screen life with through-put, it has been known to secure multiple layers of wire screen cloth to a perforated panel. The perforated panel is, in turn, secured to the frame. In the manufacturing process, the perforated panel and accompanying screens must be accurately aligned before adhesively bonding to the frame. It would be desirable to provide a self-alignment mechanism to align the perforated plate with the frame.
It is a principal object and purpose of the present invention to provide a vibrating screen assembly having a tubular frame which is both lightweight and rigid.
It is a further object and purpose of the present invention to provide a vibrating screen assembly having a frame which would position the perforated panel thereon during the assembly process and discourage separation of the frame from the perforated panel.
It is an additional object and purpose of the present invention to provide a vibrating screen assembly with a blunt, safe edge around the perimeter to prevent property damage and to prevent personnel injury.
It is an additional object and purpose of the present invention to provide a vibrating screen assembly with good adhesion between the frame and the perforated plate.
It is a further object and purpose of the present invention to provide a vibrating screen assembly that will have a maximum useful life while being simple and inexpensive to manufacture.
It is a further object and purpose of the present invention to provide a screen assembly having a strong tubular frame which will provide strength from side to side and provide strength from end to end.
One problem with existing screen assemblies is that they permit a mixture of liquid and solid particles to flow between adjoining screen frames, thereby allowing the liquid to bypass and frustrate the process described herein for separating the mixture into liquid and solid particles.
Accordingly, it is a principal object and purpose of the present invention to prevent a leakage of a mixture of liquid and solid particles between adjoining screen assemblies by providing a seal mechanism.
It is a further object and purpose of the present invention to provide a replaceable screen assembly for a vibrating shaker that is simple and quick to install and to replace.
The present invention is directed to a vibrating screen assembly having a tubular frame which includes a pair of opposed sides and a pair of opposed ends. The sides are opposed and parallel to each other. Each opposed side of the frame includes a rectangular tubular portion having a top that forms a flat planar surface.
Each side has a flat planar surface and each end has a flat, planar surface which are aligned with each other in the assembled frame. An upstanding lip extends vertically from each of the planar surfaces, the lips together defining an area forming a rim enclosure.
Finally, a ledge extends from each side parallel to the planar surfaces inwardly. The ledges are opposed to and facing each other.
The frame also includes a plurality of tubular cross supports which extend between the sides and are parallel to the ends. The tubular cross supports and the ends rest on and are attached to the ledges.
A perforated plate is attached and secured to the frame in the assembled condition. The perforated plate includes a plurality of openings which are punched or otherwise formed in the plate.
The frame is adhesively secured to the perforated plate. The plate and a plurality of accompanying screen cloths are aligned on the frame by the lips which form the rim enclosure. Each of the lips is rounded or radiused at its top to help align and guide the plate during installation.
In order to produce a vibrating screen assembly in accordance with the present invention, the sides of the frame are extruded in lengths, such as from extruded aluminum. The ends may also be fabricated from extruded aluminum. The frame sections are cut to desired lengths to form the pair of opposed sides. The ends are each notched where they are joined to the sides.
Likewise, lengths of tubular support are extruded, such as from extruded aluminum. Tubular support members are cut from these lengths to the desired dimension. The opposed sides, opposed ends, and tubular cross supports are clamped together and then welded. The joints between the cross supports and the sides of the frame and the ends and the sides of the frame are strengthened since the cross supports and ends rest on the ledges.
The perforated plate is fabricated with hexagonal or other openings and, thereafter, coated with epoxy. Both heat and pressure are used to bond the multiple screen mesh layers to the perforated plate. Accordingly, the perforated plate and the screen cloths are secured together. Thereafter, the perforated plate and the accompanying screen cloths are secured to the frame by glue or other adhesive or mechanical methods. The lips form a rim enclosure that aligns and guides the perforated plate and accompanying screen cloths on the frame. The plate is prevented from moving from side to side or end to end with respect to the frame because of the rim enclosure. The lip also provides a blunt, safe edge around the perimeter of the screen assembly which keeps personnel from cutting their hands.
Additionally, a seal mechanism is provided to seal adjoining screen assemblies. One frame end has a protruding overhang while the opposed end on an adjacent screen frame has a recess. The protruding overhang has a radiused end while the recess is likewise radiused. The protruding overhang of one frame will mate with the recess of the other frame to form a liquid-tight seal.